1. Field of the Invention
The present invention relates to a feeding and indexing apparatus for intermittently feeding articles along a circular path, and more particularly to a feeding and indexing apparatus capable of preventing the fluctuations in the load that the apparatus experiences while it is intermittently feeding articles.
2. Description of the Prior Art
One known feeding and indexing apparatus disclosed in a Japanese laid-open patent publication No. 3-192016 moves successively supplied articles along a circular path, and stops the articles at a certain angular position for inspecting or otherwise processing them.
The disclosed feeding and indexing apparatus will be described in detail below with reference to FIG. 7 of the accompanying drawings. The feeding and indexing apparatus has a plurality of spaced article feed units 2 movable along a circular path 1 and a substantially circular cam groove 3 positioned radially inwardly of and concentrically with the circular path 1. The cam groove 3 includes an arcuate portion on half of its full extent and also has an inner cam profile 3a and an outer cam profile 3b which are radially spaced from each other and have a way configuration. The inner and outer cam profiles 3a, 3b jointly have a plurality of valleys R1-R7 and a plurality of mountains R'1-R'6 alternating with the valleys R1-R7. The feeding and indexing apparatus also has a plurality of cam followers 4 in the form of rollers provided in unison with the respective article feed units 2. The cam followers 4 are movable in contact with the inner and outer cam profiles 3a, 3b.
A plurality of radial drive arms 5 rotatable about the center O of the cam groove 3 are associated respectively with the article feed units 2. More specifically, the drive arms 5 have respective radial outer ends to which respective inverted L-shaped driven arms 7 are angularly movably connected at their axes by respective rotary bearings 6. The driven arms 7 have respective hands connected to the respective cam followers 4. The driven arms 7 have respective radial hands that are operatively connected to the respective article feed units 2 by respective linear sliding bearings 8 serving as connecting members such that the distance between the rotating axes of the driven arms 7, i.e., the position of the rotary bearings 6 and the respective article feed units 2, is variable. Rotary bearings 9 are interposed between the linear sliding bearings 8 and the article feed units 2 for making the article feed units 2 rotatable with respect to the linear sliding bearings 8.
The conventional feeding and indexing apparatus shown in FIG. 7 operates as follows: The feeding and indexing apparatus receives, at a contact point T.sub.1, an article on one of the article feed units 2 from an inlet star wheel W.sub.1 that is rotating continuously. The drive arms 5 are rotating at a constant speed in the direction indicated by the arrow A. While a cam follower 4 is moving in the arcuate portion of the cam groove 3, the article feed unit 2 associated with the cam follower 4 moves along the circular path 1 at a constant speed. As the cam follower 4 approaches the valley R1 in the wavy configuration of the cam groove 3, the driven arm 7 is angularly moved counterclockwise about the rotary bearing 6 with respect to the drive arm 5. Therefore, the driven arm 7 is tilted further forwardly along the circular path 1 from a radially outward extension of the drive arm 5. The article feed unit 2 approaches a stop position S.sub.1 and hence is decelerated. The article feed unit 2 is stopped when it reaches the stop position S.sub.1.
When the drive arm 5 and the radial hand of the driven arm 7 are radially aligned with each other, they are in a central position during an interval in which the article feed unit 2 is in the stop position S.sub.1. The article feed unit 2 remains in the stop position S.sub.1 so long as the drive arm 5 is positioned within an angular range .alpha. across the central position.
While the driven arm 7 is angularly moving about the stop position S.sub.1, the article feed unit 2 continues to remain at rest in the stop position S.sub.1. During angular movement of the driven arm 7 about the stop position S.sub.1, the distance between the article feed unit 2 and the rotating axis of the driven arm 7 (the position of the rotary bearing 6) varies, and the variation in the distance is compensated by the linear sliding bearing 8 that connects the article feed unit 2 to the driven arm 7. The cam follower 4 approaches the peak of the mountain R'1 upon further rotation of the drive arm 5, and the article feed unit 2 starts leaving the stop position S.sub.1. Continued movement of the cam follower 4 past the mountain R'1 toward the valley R2 causes the article feed unit 2 to approach the radially outward extension of the drive arm 5, i.e., to be accelerated. When the drive arm 5 is superposed on the mountain R'1, the speed of the article feed unit 2 is maximum.
Thereafter, the article feed unit 2 moves toward a next stop position S.sub.2, and repeats the above operation. After the article feed unit 2 moves past a last stop position S.sub.7, the article feed unit 2 is accelerated. Then, the article feed unit 2 moves at a constant speed, and discharges the article onto an outlet star wheel W.sub.2 at a contact point T.sub.2.
In the conventional feeding and indexing apparatus, a pitch angle .theta..sub.1 formed at the center O between adjacent mountains or valleys of the cam groove 3 is equal to a pitch angle .theta..sub.2 formed at the center O between adjacent junction points of the drive arms 5 and the driven arms 7 (adjacent rotary bearings 6). Therefore, all the article feed units 2 start from and stop at synchronously at the stop positions S.sub.1 -S.sub.7. As a result, the load imposed on the feeding and indexing apparatus varies greatly between start and stop times, and hence tends to vibrate during operation thereof. Such vibration is detrimental to any processing operation effected on articles carried by the article feed units 2, and deters the feeding and indexing apparatus from being operated at high speed. Furthermore, the durability of the feeding and indexing apparatus is impaired when it is subject to vibrations. If the articles carried by the article feed units 2 are inspected at the respective stop positions S.sub.1 -S.sub.7, then the inspecting procedure is adversely affected by the vibration of the feeding and indexing apparatus. Consequently, there has been a need to prevent the feeding and indexing apparatus from vibrating.